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Page Title:
Primary Power Source 26.5-volt dc. |
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|  TM 11-5820-509-35
(2) Primary Power Source 26.5-volt dc.
Item
Indication
Probable trouble
Procedure
NOTE
Place the POWFR-LIGHTS switch on the front of RT-671/PRC-47 to POWER ON.
1
Dc voltage measured between
a.
Fuse F1 (POWER 20A DC) is
a.
Check and replace fuse F1 (fig.
A5J9 (fig. 3-4) and chassis
blown or primary power circuit
3-87). Check continuity of input
ground is not +26.5 volts dc.
is defective.
at L4; replace L4 if open. Check
Note. Do not perform this test if
capacitors C26 and C27 for
115-volts, 400-Hz primary power
shorts; replace if shorted.
source is being used to power
b. +6.5 volts dc is not present at
b.
Check continuity from F1
the equipment. Use previous
the coil of relay K1 (terminals
holder to K1-1 and K1-4, and to
chart (1).
K1-1 to K1-4.)
connector P1-J. Repair if open.
c.
Check continuity of CR8 and
defective.
R16 for opens and shorts to
ground. Replace defective
component.
d.
POWER-LIGHTS switch on
d.
Check continuity from K2-5 to
front panel, or associated circuit
chassis ground with POWER-
defective.
LIGHTS switch at POWER-
ON. Repair circuit or replace
switch.
e.
Dc power control relay K1 coil
e.
Replace K1 if winding
defective.
resistance is not 1628 10%
ohms.
f.
Contacts of K1 are defective.
f.
Check dc voltage at K1-7 with
POWER-LIGHTS switch to
POWER ON. Replace K1 if
reading is zero volts.
g.
Dc circuit from K1 to PP-
g.
Check continuity from K1-7 to
3518/PRC47 is defective.
connector J1-22; and each point
for short to ground. Repair as
required.
2
Transmitter bias and high-voltage
a.
Circuit to high-voltage trans-
a.
Remove front panel power plug
output is low or zero when 26.5-
former A5T1 in PP-3518/PRC-
and check continuity from J1-14
volt dc primary power input is
47 is defective.
to J1-1; repair primary circuit to
used, but normal with 115-volt,
A5T1 or replace transformer.
400-Hz primary power source.
b.
Contacts of push-to-talk relay
b.
Check voltage at A5K1-5 with
A5K1 are defective.
ptt relay operated: (normal
+26.5 volts dc). Replace A5K1
if no voltage present.
c.
Circuit between J1 and power
c.
Check continuity of power cable
oscillator defective.
jumpers (pins A-B. C-D, and J-
K) and circuits from J1-1/J1-2,
J1-14/J1-15, and J1-16/J1-17;
repair circuit or replace cable.
Check continuity from P1-A to
Q2 emitter, and from P1-C to Q1
emitter; repair circuit if open.
d.
Emitter circuit components
d.
Check continuity of C1, CR1,
defective.
CR2, and R5 for opens and
shorts: replace defective com-
ponent.
e.
Base circuit components
e.
Check continuity of R1 through
defective.
R4: replace defective component.
Check winding of reactor for
opens: normal readings are T1-1
to T1-2, 1.0 ohm: T1-2 to T1-3,
60 ohms: T1-3 to T1-4 1.0 ohm;
replace T1 if defective.
f.
Power transistors Q1 and Q2
f.
Replace with proper type
defective.
number.
3-76
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